Lift trucks, construction equipment, farm tractors, and similar vehicles frequently are manufactured with overhead guard or cage-like structures to protect the driver/operator from injury from falling objects or overturning of the vehicle. Typically, these guards are ruggedly constructed and may be welded directly to the frame, subframe or platform of the vehicle and in such cases are not readily removable from the frame or subframe. Often, a vehicle will be destined for use in an environment that is hostile to the operator. Adverse conditions for the operator include operation in excessively warm or cold environments, rain, dust and the like. In these and other conditions, it is common to provide a cab or enclosure on the vehicle to protect the driver from exposure. The cabs, known in the prior art, can range from simple weatherproof fabric and vinyl covers attached to the overhead guard to sophisticated sheet metal structures with safety glass windshields, side lights and an overhead light. In many instances, metal cabs have been constructed with sufficient rigidity to serve for overhead protection in place of an overhead guard originally fitted or specified on the vehicle. Where the overhead guard originally supplied on a vehicle is fabricated as a weldment that is integrated with the frame or platform of the vehicle it may not be practical to remove the overhead guard and replace it with a self-supporting cab. It is known to construct a cab by assembling panels on an overhead guard but as far as is known this approach has had limited success because of the high labor content that results from the effort and skill required to produce prior art assemblies with acceptable quality and finish.